A new documentary provides a detailed look at the inner workings of Mexico’s Sinaloa Cartel, from mules loaded down with sacks of marijuana to the methamphetamine cooks working on the outskirts of Culiacán.

Spanish journalist David Beriain spent weeks in northwest Mexico, documenting his interactions for the Discovery en Español show “Clandestino.”

The result is three 45-minute episodes, which are available on YouTube, that take him from the capital of Sinaloa to just north of the U.S. border, always in the company of his cameraman and one or more members of what has long been considered Mexico’s most powerful criminal organization.

Beriain emphasizes at the outset of his documentary that some unnamed authority within the organization has blessed his project. Armed with that endorsement, he accompanies a seemingly endless stream of cartel members as they go about their jobs, and engages each of them in an interview lasting five or eight minutes.

The subjects aren’t intimate friends with Jesus “El Mayo” Zambada or Joaquín “El Chapo” Guzmán, though their jobs are demonstrably impacted by the recent attacks on the group’s leadership.

Beriain’s method as an interviewer is simple and effective — he asks each of the employees about what exactly they do, and then he asks them why they do it.

Many of Beriain’s queries are quite basic. “What is that stick for?” he asks the keeper of a safehouse at one point. He focuses a great deal on the sequences of their chores, and also on the consequences of the mistakes. This provides viewers with an extremely granular understanding of precisely what it entails to serve as the Sinaloa Cartel’s armament technician, or as the cultivator of a heroin field, or as a torturer.

“Clandestino” also shines when it tackles the moral compromises of working in the drug trade. Beriain does not shy away from asking people if they are personally responsible for harming others. He asks virtually all his interviewees how they feel about the uglier side of their trade, from beating people and risking their lives to profiting off of addiction and enabling murder.

The answers are often illustrative.

Some recoil from the choices they’ve made, while others embrace their ability to inflict pain. At least two describe the Sinaloa Cartel in moralistic terms, as the one gang that refuses harm the civilian population.

One of the most affecting portions of the film was a dirty cop, expressing some mixture of resignation and shame, explaining how he came to work for the group he’s theoretically paid to combat.

Discovery en Español capture

Virtually all of the members of the cartel point to money as their chief motivator. This line of questioning tends to lead to further disclosures about their pay scale.

A woman charges $4,000 to fly with a half kilogram of heroin, contained in a tube hidden in her vagina, to Tijuana from points further south in Mexico. The leader of a team that drives a truck laden with drugs through the Tijuana border crossing receives $6,000. For the mule who carries loads of marijuana through the desert on foot, a trip that could last up to eight days, $2,000 awaits.

The data about salaries is just one of a series of unusually penetrating insights about the economics of the Sinaloa Cartel’s operations revealed in “Clandestino.”

Beriain observes early in the program that the gang’s privileged position derives from its control of the western half of the U.S. border, similar to the way a legitimate company seeks to exploit its own unique assets, from productive oil fields to irreplaceable computer processors. Controlling access to the world’s largest drug market has made the Sinaloa Cartel the single most important gatekeeper in the world of organized crime.

Viewers also learn that the cartel operates as a sort of regulator for all manner of illegal activities. It fixes the retail and wholesale price for drugs within its territory, and it prohibits certain activities like extortion, kidnapping and rape, we are told.

The Sinaloa Cartel is striking in its employees’ degree of specialization. Each member has one basic task — physically moving drugs across a single route, maintaining weapons, producing a single drug, guarding a safe house, picking up drugs in the United States, patrolling Culiacán in search of rival bands or executing rivals.

The members profess little awareness of other elements of the gangs’ operations, but all know their own work quite well.

The organization is in some senses like an assembly line stretching across the whole of northwestern Mexico. This makes it both extremely productive and extremely resilient.

The individuals who appear in “Clandestino” are capable of moving hundreds of pounds a day of heroin, marijuana and cocaine across the U.S. border, something approaching industrial scale. They operate essentially in unison, forming one single organism.

But the gang is largely cellular in its operation, and attacking one part of the organism — for example, the gunmen in Culiacán — has little impact on another, such as the specialists who prepare hidden compartments for cars.

Despite its many positive qualities, it’s fair to lodge a few criticisms of “Clandestino.” The pulse-pounding music and the constant reminders of danger would not feel out of place in a low-budget thriller movie.

And as effective as it is, Beriain’s formula in dealing with this succession of gangsters grows slightly redundant over the course of the two hours of filming.

Moreover, while the breadth of the Sinaloa Cartel’s portrayal is perhaps unprecedented, as characters, none of the people who appear before Beriain’s camera quite come alive. There is no one, for instance, who will etch themselves into viewers’ memories the way José Manuel Mireles did in “Cartel Land.”

Nevertheless, “Clandestino” is incisive, original, informative, and entertaining. It is among the most thorough cinematic treatments that one of the world’s most important criminal groups has ever received.